Arc-fault interruption (AFI) and ground-fault interruption (GFI) circuit breakers are well known. Such circuit breakers have traditionally required an extra conductor, called a “pigtail,” or neutral to connect the breaker to a neutral conductor of an electrical distribution panel or load center (these terms are used interchangeably herein). Increased use of arc-fault circuit breakers in a residential load center results in additional pigtails crowding the wiring gutter of the load center, making it more difficult to wire as more circuit breakers are added and creating a jumble of wires. Furthermore, to wire the pigtail, the installer must connect the wire at the side neutral conductor using a tool, thereby making the wiring more time consuming.
More recently, AFI and GFI circuit breakers feature a “plug-on neutral” (PON or PoN), which replaces the pigtail, and allows the circuit breaker to be “plugged onto” the neutral bus bar directly. Instead of a pigtail, the circuit breaker has a connector called a plug-on neutral (PON) clip that directly plugs onto the neutral conductor of the electrical distribution panel. The PON clip typically faces downward away from a bottom surface of the plug-on neutral type circuit breaker so that it is oriented to be plugged directly onto a neutral conductor in the electrical distribution panel. However, certain disadvantages remain when accommodating plug-on neutral type circuit breakers as well as pigtail circuit breakers in the same panel because both circuit breaker types are widely used.
For example, one known type of hybrid neutral bus bar utilizes a square screw down rail, which has a flat and even top surface with minimally spaced wire landing holes for receiving hold down screws for use with a wire type circuit breaker or on which to secure a plug-on neutral clip of a PON type circuit breaker. In order to make a plug-on neutral connection any screw below the PON clip must either be removed or tightened completely to avoid incidental damage to the PON clip if it is removed in a typical rotary fashion. In addition, to plug on over a hold down screw, the PON type circuit breaker must be designed with an overly large PON clip that does not install in a familiar revolute motion. Furthermore, the referenced square rail neutral bus bar is designed with minimally spaced wire landing holes to place as many wire landing holes and hold down screws on the neutral bus bar. However, the wire landing holes are not matched in any way to the pole spacing for circuit breakers connectable onto an electrical distribution panel. As a consequence, the neutral bus bar number of wire landing holes significantly exceeds the requirement for hold down screws, which makes it difficult to trace the circuit breakers on the panel to their connection point on the neutral bus bar.